This invention relates generally to implantable electrical leads and more particularly for implantable leads intended for use in the coronary sinus of a patient's heart.
Recently there has been an increased interest in the placement of cardiac pacing and sensing electrodes in the coronary sinus, particularly for purposes of bi-atrial and bi-ventricular pacing. In this context, a number of configurations have been proposed in order to assist in placement and retention of the lead and its electrodes in desired locations within the coronary sinus. Early coronary sinus leads such as the Medtronic Model 6992 Lead had a generally straight lead body configuration and employed a non-conductive tip extending distally from the distal-most electrode as a mechanism for assisting in the insertion of the lead in the coronary sinus and for retaining it in the coronary sinus after insertion. More recently, it has been proposed to provide a body of a coronary sinus lead with a pre-formed sinusoidal or helical configuration in order to allow the lead to expand into contact with the walls of the coronary sinus and thereby retain the lead, much in the same fashion as has been employed in the context of spinal stimulation leads. Coronary sinus leads having such a pre-formed configuration are disclosed in U.S. Pat. No. 5,423,865 issued to Bowald et al. and U.S. Pat. No. 5,476,498 issued to Ayers. Spinal cord stimulation leads having similar pre-formed configurations are disclosed in U.S. Pat. No. 4,374,527 issued to Iversen and U.S. Pat. No. 4,414,986 issued to Dickhudt.
An alternative approach to fabrication of coronary sinus leads has been to provide the distal portion of the lead with a curved configuration corresponding to some extent to the curved configuration of the coronary sinus and great vein. For example, a coronary sinus lead having a continuous multi-radius curvature is disclosed in U.S. Pat. No. 5,433,729 issued to Adams et al. Similar configurations are illustrated in U.S. Pat. No. 5,423,772 issued to Lurie and in U.S. Pat. No. 5,445,148 issued to Jaraczewski. An alternative configuration employing two spaced 45.degree. bends is disclosed in U.S. Pat. No. 5,683,445 issued to Swoyer.